The present invention relates to a vacuum fluorescent display which emits light by bombarding electrons emitted from a field emission type electron-emitting source against a phosphor.
Conventionally, as a display component for an audio apparatus or automobile dashboard, a vacuum fluorescent display is one type of electronic display device frequently used. In the vacuum fluorescent display, an anode attached with a phosphor and a cathode are arranged in a vacuum vessel to oppose each other, and electrons emitted from the cathode are bombarded against the phosphor to emit light. As a general vacuum fluorescent display, a triode structure is used most often, in which a grid for controlling the electron flow is provided between the cathode and anode, so the phosphor selectively emits light.
Recently, to greatly increase the luminance of the vacuum fluorescent display, a vacuum fluorescent display in which a field emission type electron-emitting source using carbon nanotubes is used as a cathode is proposed. FIG. 7 shows a conventional vacuum fluorescent display. Referring to FIG. 7, the conventional vacuum fluorescent display has an envelope 300 constituted by a front glass member 301 which has light transmission properties at least partly, a substrate 302 opposing the front glass member 301, and a frame-like spacer 303 for hermetically connecting the edges of the front glass member 301 and substrate 302. The interior of the envelope 300 is vacuum-evacuated.
In the envelope 300, a plurality of front surface support members 304 vertically stand on the inner surface of the front glass member 301 to be parallel to each other at a predetermined interval. Each light-emitting portion 310 constituting a display pixel is formed on a corresponding region on the inner surface of the front glass member 301 which is sandwiched by the front surface support members 304. The light-emitting portion 310 is constituted by a band-like phosphor film 311 formed on the inner surface of the front glass member 301 and a metal back film 312 formed on the surface of the phosphor film 311 and used as an anode.
A plurality of substrate support members 305 vertically stand on the substrate 302 to oppose the front surface support members 304. A plurality of band-like wiring electrodes 320 are formed in regions on the inner surface of the substrate 302 each of which is sandwiched by the substrate support members 305 to oppose the respective light-emitting portions 310. Field emission type electron-emitting sources 330 made of carbon nanotubes are formed on the wiring electrodes 320, respectively. Further, a plurality of mesh-like electron extracting electrodes 340 are arranged to be spaced apart from the field emission type electron-emitting sources 330 by a predetermined distance. The electron extracting electrodes 340 are formed in the direction perpendicular to the field emission type electron-emitting sources 330 to have a band-like shape, and arranged to be parallel to each other at a predetermined interval. The electron extracting electrodes 340 are sandwiched and fixed between the substrate support members 305 and front surface support members 304.
The operation of the vacuum fluorescent display will be described next with reference to FIG. 8. Note that the support members 304, and the support members 305, arranged between the electrodes are not shown in FIG. 8. Referring to FIG. 8, the field emission type electron-emitting sources 330 are arranged to be parallel to each other at a predetermined interval, and the electron extracting electrodes 340 are arranged above the field emission type electron-emitting sources 330. The electron extracting electrodes 340 are formed in the direction perpendicular to the field emission type electron-emitting sources 330 and arranged to be parallel to each other at a predetermined interval. The plurality of light-emitting portions 310 are arranged above the electron extracting electrodes 340 at positions opposing the respective field emission type electron-emitting sources 330.
A positive voltage (accelerating voltage) is applied to the metal back films 312 of the light-emitting portions 310. In this state, in the vacuum fluorescent display, voltages applied to each field emission type electron-emitting source 330 and each electron extracting electrode 340 switch the ON/OFF states of a corresponding one of the light-emitting portions 310 which opposes the intersecting region of the field emission type electron-emitting source 330 and electron extracting electrode 340. In this vacuum fluorescent display, when 0 V is applied to the electron extracting electrode 340, an electric field required for emitting electrons is not generated in the field emission type electron-emitting sources 330. Accordingly, the light-emitting portion 310 becomes an OFF state 310a independently of a voltage applied to the field emission type electron-emitting source 330.
When a predetermined positive voltage is applied to the electron extracting electrode 340, a voltage applied to each field emission type electron-emitting source 330 through a corresponding one of the wiring electrodes 320 can switch the ON/OFF states of a corresponding one of the light-emitting portions 310 which opposes the intersecting region of the field emission type electron-emitting source 330 and electron extracting electrode 340. In this case, when a voltage applied to the field emission type electron-emitting source 330 is 0 V, the light-emitting portion 310 becomes an ON state 310b, and when a predetermined positive voltage is applied to the field emission type electron-emitting source 330, the light-emitting portion 310 becomes the OFF state 310a. Accordingly, in this vacuum fluorescent display, scanning is performed such that the positive voltage is sequentially applied to the respective electron extracting electrodes 340, and in synchronism with this scanning, voltages applied to the respective field emission type electron-emitting sources 330 are switched in correspondence with the respective pixels to be displayed, thereby performing matrix display.
In the conventional vacuum fluorescent display, however, the electron-emitting sources are formed on the substrate. Therefore, when faults such as a luminance nonuniformity and the like have been found in the electron-emitting source, the substrate itself must be discarded, thereby causing a decrease in manufacturing yield.
It is an object of the present invention to provide a vacuum fluorescent display using a field emission type electron-emitting source which increases the manufacturing yield.
In order to achieve the above object, according to the present invention, there is provided a vacuum fluorescent display comprising a front glass member which has light transmission properties at least partly, a substrate opposing the front glass member through a vacuum space, a control electrode formed on an inner surface of the substrate, a plate-like field emission type electron-emitting source with a plurality of through holes which is arranged in the vacuum space to be spaced apart from the control electrode, a mesh-like electron extracting electrode formed between the field emission type electron-emitting source and the front glass member to be spaced apart from the field emission type electron-emitting source, and a phosphor film formed inside the front glass member.